Will I hurt myself if I drink alcohol while I'm taking zoloft (sertraline)?

Maybe. Every drop of alcohol is a depressant, and you are taking an antidepressant---that doesn't make sense. Also, there are isolated reports of patients having blackouts with very little alcohol.
No. Zoloft, or sertraline, is an anti-depressant/anti-anxiety medicine that works on the brain chemical serotonin. In general if you have problems with depression or anxiety, alcohol is likely to worsen your symptoms and make medications like sertraline less effective. So it doesn't hurt you, it just decreases or eliminates the effectiveness of your medicine.